Chitosan–sodium alginate hydrogels incorporating amino acid-derived ionic liquids as antimicrobial agents

Polysaccharide-based hydrogels have been investigated for cutaneous applications owing to their biocompatibility, biodegradability, and ability to provide a favorable environment for wound healing. In this study, chitosan–sodium alginate (CS/Alg) hydrogels incorporating ionic liquids (ILs) derived from the decyl-1-methylimidazolinium cation ([DEC(MIM)] + ) and the amino acid anions glycine ([GLY] − ) or lysine ([LYS] − ) were developed and characterized. The effects of IL on the rheological properties and antimicrobial activity were evaluated. The formulations remained physically stable throughout the storage period while maintaining a skin-compatible pH (4.5). Scanning electron microscopy revealed irregular and porous structures favorable for topical adhesion and bioactive compound loading. Furthermore, IL incorporation increased the viscosity and mechanical strength of the CS/Alg hydrogels. Optimal rheological properties were observed for formulations containing 10% [DEC(MIM)][GLY] and 5% [DEC(MIM)][LYS]. Formulations containing 15% [DEC(MIM)][GLY] and 10–15% [DEC(MIM)][LYS] exhibited pronounced bacteriostatic and bactericidal activities. The Hen's egg chorioallantoic membrane (HET-CAM) assay indicated suitability for superficial topical application. The 1 H NMR chemical shift analysis was consistent with intermolecular interactions between ILs and polymers, which may contribute to hydrogel structuration and mechanical resistance. Overall, IL incorporation significantly influenced the physicochemical and biological properties of CS/Alg hydrogels, highlighting their potential for topical pharmaceutical applications.